CA2543647A1

CA2543647A1 - Vaso-occlusive devices with bioactive elements

Info

Publication number: CA2543647A1
Application number: CA002543647A
Authority: CA
Inventors: Stephen C. Porter
Original assignee: Individual
Current assignee: Boston Scientific Ltd Barbados
Priority date: 2003-10-27
Filing date: 2004-10-08
Publication date: 2005-05-19
Also published as: EP1677847A1; WO2005044324A1; JP2007523055A; US20050090856A1

Abstract

Vaso-occlusive devices for occluding a body cavity include an internal element located within a lumen of the device. The internal element may comprise or otherwise include an agent carrier that comprises a bioactive material capable of eliciting a biological reaction after the device is placed in-situ. For example, the bioactive material can be a part of a composition of the agent carrier, absorbed by the agent carrier, or coated as a layer on the agent carrier.

Description

VASO-OCCLUSIVE DEVICES WITH BIOACTIVE ELEMENTS
FIELD OF INVENTION
The invention pertains to medical devices, and more particularly to vaso-occlusive devices with internal biologically active agents.
BACKGROUND
In many clinical situations, blood vessels are occluded for a variety of purposes, such as to control bleeding, to prevent blood supply to tumors, and to block blood flow within an aneurysm, arteriovenous malformation, or arteriovenous fistula.
Vaso-occlusive devices are surgical implants placed within blood vessels or vascular cavities, typically by using a catheter as a conduit, to arrest blood flow, form a thrombus and occlude the site. For instance, a stroke or other such vascular occurrence may be treated by placing a vaso-occlusive device proximal of the site to block the flow of blood to the site and alleviate the leakage. An aneurysm may similarly be treated by introducing one or more vaso-occlusive devices through the neck of the aneurysm. The placement of the vaso-occlusive devices) helps cause a mass to form in the aneurisrnal sac and alleviate the potential for growth of the aneurysm and its subsequent rupture. Other diseases, such as tumors, may often be treated by occluding the blood flow to the tumor.
There are a variety of known vaso-occlusive devices suitable for creating an embolic obstruction for therapeutic purposes. One such device is a vaso-occlusive coil that assumes a linear helical configuration when stretched and a folded convoluted configuration when relaxed. The coil has a stretched configuration when placed in a catheter, which is used in placement of the coil at the desired site, and assumes the convoluted configuration when the coil is ejected from the catheter and the coil relaxes.
It is known to coat vaso-occlusive devices with a bioactive material that enhances a thrombogenic characteristic of the device, or that promotes conversion of thrombus to cellular tissues. For example, U.S. Patent No.
6,2~0,457B1 to Wallace et al., describes an occlusive device including an inner core wire covered with a polymeric material. The polymeric material includes protein based polymers, absorbable polymers, non-protein based polymers, and combinations thereof. The polymer facilitates the processes of thrombosis within a body cavity andlor conversion of thrombus into dense cellular tissue to stabilize the occlusion of a body cavity. However, the coating of bioactive material may increase friction between the occlusive device and an occlusive device delivery tool during deployment of the occlusive device. In some cases, the coating may even cause the occlusive device to adhere to the delivery tool or to a packaging. The coating of bioactive material may also alter a mechanical behavior of the occlusive device.
SUMMARY OF THE INVENTION
A vaso-occlusive device having an agent delivery capability is provided. In one embodiment, the vaso-occlusive device includes a coil and an agent carrier disposed within a lumen of the coil. The agent carrier includes a bioactive material or agent that elicits a tissue reaction when placed inside a body. By way of non-limiting examples, the agent carrier can have an elongate shape, be in a form of a sphere, a cone, a plate, a mesh, or other customized shape. The agent carrier can be made from a biodegradable material, in which case, the composition of the agent carrier includes a bioactive material or agent that is released when placed inside a body. The agent carrier can also be made from a non-biodegradable material, in which case, the bioactive material or agent is coated onto a surface of or incorporated within the agent carrier. In other embodiments, the agent carrier is made from a material that adheres or absorbs a bioactive agent. By way of non-limiting examples, the agent carrier can include one or more polymer filaments, a sponge, a tube, a cloth, or other materials that are capable of encompassing, absorbing or adhering a bioactive agent. In this case, the agent carrier is used to deliver the bioactive agent, which will diffuse out of the agent carrier into the surroundings when placed in a target site.
One advantage of this embodiment is that placing the agent carrier within the lumen of the coil allows an exterior of the coil to be unaffected by the bioactive material during delivery of the coil.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
FIG. 1 is a side view of a vaso-occlusive device 10 constructed in accordance with one embodiment of the invention. The vasso-occlusive device 10 is provided with an agent carrier 14 carried by the coil 12. The coil 12 is made from a linear element 16, such as a wire, which preferably has a circular cross-sectional shape. In alternative embodiments, the linear element 16 of the coil 12 may have a rectangular, triangular, other geometric cross-section, or an irregular shaped cross-section. The coil 12 includes one or more loops or windings 18 formed by the linear element 16. The loops 18 define a central lumen 20 in which the agent carrier 14 is placed. In the illustrated embodiment, the vaso-occlusive device 10 has an overall diameter or cross-section which is preferably in the range of 0.010 to 0.023 inches.
However, the vaso-occlusive device 10 may have other diameters and/or cross-sections, as well.
The vaso-occlusive device 10 may optionally include one or more end caps 22 secured to a first end 24 or to a first and a second end 26 of the coil 12.
The coil 12 may have an open or closed pitch, and may be constructed by wrapping the linear element 16, such as a wire, around a mandrel, stylet, or other shaping element. The coil 12 may optionally be heat treated, as known to one skilled in the art. It should be noted that the formation of vaso-occlusive devices having a helical coil shape is well known in the art, and need not be described in further detail.
The coil 12 may be made of a variety of materials, such as metals or polymers. Suitable metals and alloys for the coil 12 may include the Platinum Group metals, especially platinum, rhodium, palladium, rhenium, as well as tungsten, gold, tantalum, and alloys of these metals. These metals have significant radiopacity and their alloys may be tailored to accomplish an appropriate blend of flexibility and stiffness. These metals are also largely biologically inert. The coil 12 may also be formed from stainless steels if some sacrifice of radiopacity may be tolerated. Other materials that may be used may include "super-elastic alloys," such as nickel/titanium ("Nitinol") alloys, copper/zinc alloys, or nickel/aluminum alloys. If Nitinol is used, the diameter of the coil 12 may be significantly smaller than that of a coil 12 made from relatively more ductile platinum or platinum/tungsten alloy.
Examples of polymers that may be used for construction of the coil 12 includes polydienes, polyalkenes, polystyrenes, polyoxides, polycarbonates, polyesters, polyanhydrides, polyurethanes, polyamides, polyimides, polyacrylics, polymethacrylics, polyacetals, and vinyl polymers. The coil 12 can alternatively be made of radiolucent fibers or polymers, such as Dacron (polyester), polyglycolic acid, polylactic acid, fluoropolymers (polytetrafluoroethylene), Nylon (polyamide), and/or silk.
If the coil 12 is not made from a radiopaque material, the coil 12 may be coated, mixed, or filled with radiopaque materials such as metals (e.g.
tantalum, gold, tungsten or platinum), barium sulfate, bismuth oxide, bismuth subcarbonate, zirconium oxide, and the like. Alternatively, continuous or discrete radiopaque markers may be incorporated within or affixed to the coil 12.
The agent carrier 14 includes one or more axially oriented elements 30 having a substantially rectilinear or a curvilinear (less than 360°) configuration along a length of the vaso-occlusive device 10. In the case of a more complex coil shape, the active element could mirror the shape of the coil. The axially oriented element 30 is located within the lumen 20 of the coil 12 and is secured to the ends 24 and 26 or the end caps 22 of the coil 12. The securing may be accomplished by an anchor or a suitable adhesive, such as ultraviolet-curable adhesives, silicones, cyanoacrylates, or epoxies.
Alternatively, the axially oriented element 30 can be secured to the coil 12 by chemical bonding between reactive groups on the axially oriented element 30 and the coil 12, solvent bonding, fusing both materials so that they melt together, or temporarily melting the surface of the coil 12 to embed part of the axially oriented element 30.
An advantage of securing the axially oriented element 30 to both ends 24 and 26 of the coil 12 is that the axially oriented element 30 can function as a stretch-resistant member, which prevents the first end 24 of the coil 12 from being pulled too far from the second end 26. The axially oriented element 30 can also be pre-stretched before it is secured to the ends of the coil 12, to thereby provide some degree of compression within the coil 12.
In alternative embodiments, instead of securing to both ends of the coil 12, the axially oriented element 30 can be secured to the coil 12 at one of the ends 24 and 26 of the coil 12 or at one or more points along a length of the coil 12 by a suitable adhesive or by wrapping around one or more windings 18 of the coil 12. In another embodiment, the axially oriented element 30 is not secured to the coil 12, but is simply disposed within the lumen 20 of the coil 12, or is coupled to the coil 10 by a surface friction, in which case, the surface of the axially oriented element 30 may be textured to improve the coupling force between the axially oriented element 30 and the coil 12.
The agent carrier 14 preferably has a cross-sectional dimension such that the overall flexibility of the vaso-occlusive device 10 is not significantly impacted. In one embodiment, the cross-sectional dimension of the agent carrier 14 is approximately 0.002 inch less than the internal diameter of the coil 12. However any diameter smaller than the coil internal diameter may also be used. If the agent carrier 14 is also used as a stretch-resistant member, the agent carrier 14 should have a minimum cross-sectional dimension such that the agent carrier 14 can have enough strength to provide some degree of tensile resistance to a stretching of the coil 12.
The agent carrier 14 includes a bioactive material or agent, such as a thrombogenic or a therapeutic agent, that induces a tissue reaction when placed within a body. Particularly, the agent carrier 14 is made from a bioactive material or agent that is absorbable or biodegradable. When the vaso-occlusive device 10 is placed in a body, the agent carrier 14 dissolves and releases the agent to its surrounding environment. Alternatively, the agent carrier 14 can be made from a non-biodegradable material, in which case, a coating that comprises a bioactive agent is then deposited on a surface of the agent carrier 14. When the vaso-occlusive device 10 is placed within an aneurysm, a body temperature and/or a reaction with a bodily fluid causes the coating to degrade or dissolve, thereby releasing the bioactive agent.
Notably, the bioactive agent may be incorporated within the agent carrier, e.g., in a cavity, or dispersed within the material comprising the agent carrier itself, such material being either absorbable or non-absorbable.
Preferably, the bioactive agent is a type which elicits a tissue reaction that leads to rapid in-growth of fibro-cellular tissue, thereby stabilizing the occlusion of the aneurysm without compromising blood flow in the native vasculature. An advantage of placing the agent carrier 14 within the lumen 20 of the coil 12 is that an exterior of the coil 12 is unaffected by the bioactive material during delivery of the coil 12. That is, the bioactive material would not increase a friction between the coil 12 and a delivery tool, and would not cause the coil 12 to be adhered to the delivery tool or to a packaging.

Examples of materials that can be included in the agent carrier 14 include homopolymers or copolymers comprising in part: polyesters, acrylics, polyethers, polysiloxanes, polyurethanes, polycarbonates, and other biocompatible polymers. Biodegradable or absorbable materials may also be used in the agent carrier and/or as the bioactive agent and include, but are not limited to, synthetic polymers, polysaccharides, and proteins. Suitable polymers may include,'for example, polyglycolic acid, polylactic acid, polycaprolactone, polyhydroxyalkanoates (such as polyhydroxybutyrate and polyhydroxyvalerate), polydioxanone, poly(trimethylene carbonate), polyanhydrides, poly(g-ethyl glutamate), poly(DTH iminocarbonate), poly(bisphenol A iminocarbonate), polyarylates, polyamino acids and copolymers or mixtures thereof.
In addition, or alternatively, proteins may be used, such as collagen, elastin, caesin, fibrin, fibrinogen, fibronectin, vitronectin, laminin, silk, and/or gelatin. In addition or alternatively, polysaccharides may be used, such as chitin, chitosan, cellulose, alginate, hyaluronic acid, and chondroitin sulfate.
Many of these materials are commercially available. Fibrin-containing compositions are commercially available, for example from Baxter Healthcare.
Collagen-containing compositions are commercially available, for example, from Cohesion Technologies, Inc., of Palo Alto, California. Fibrinogen-containing compositions are described, for example, in U.S. Patent Nos.
6,168,788 and 5,290,552. As will be readily apparent, absorbable materials may be used alone or in any combination with each other. The absorbable material may be a mono-filament or multi-filament strands or a tube.

The materials that comprise the carrier can themselves be bioactive.
These materials in their unaltered or in a degraded form may stimulate a biological reaction that ultimately results in the formation of fibro-cellular tissues. For example, certain polymers such as bioabsorbable polymers or certain polyesters can illicit an inflammatory reaction; certain proteins such as fibrinogen or collagen can illicit a thrombogenic reaction; and other proteins such as silk can illicit an immune response.
Other examples of bioactive materials that can be included in the agent carrier 14 include cytokines; extracellular matrix molecules (e.g., collagen, fibrin, or decellularized animal tissues); matrix metalloproteinase inhibitors;
trace metals (e.g., copper); other molecules that may stabilize thrombus formation or inhibit clot lysis (e.g., proteins, including Factor XIII, a2-antiplasmin, plasminogen activator inhibitor-1 (PAI-1 ), and the like); and their functional fragments (e.g., the P1 or P2 epitopes of fibrin). Examples of cytokines that may be used alone or in combination with other compounds may include basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-~), and the like. Cytokines, extracellular matrix molecules, matrix metalloproteinase inhibitors, and thrombus stabilizing molecules are commercially available from several vendors, such as Genzyme (Framingham, MA), Genentech (South San Francisco, CA), Amgen (Thousand Oaks, CA), R&D Systems, and Immunex (Seattle, WA).
Additionally, bioactive polypeptides that may be synthesized recombinantly as the sequence of many of these molecules are also available, for example, from the GenBank database. Thus, the agent carrier 14 may include use of DNA or RNA encoded bioactive molecules.
Furthermore, molecules having similar biological activity as wild-type or purified cytokines, extracellular matrix molecules, matrix metalloproteinase inhibitors, thrombus-stabilizing proteins (e.g., recombinantly produced or mutants thereof), and nucleic acid encoding these molecules may also be used. The amount and concentration of the bioactive materials that may be included in the composition of the agent carrier 14 may vary depending upon the specific application. It will be understood that any combination of materials, concentration, and/or dosage may be used, so long as it is not harmful to the subject.
The structural materials that comprise the carrier can themselves be the bioactive agent. These materials in their unaltered or in a degraded form may stimulate a biological reaction that ultimately results in the formation of fibro-cellular tissues. For example, certain polymers such as bioabsorbable polymers or certain polyesters can illicit an inflammatory reaction; certain proteins such as fibrinogen or collagen can illicit a thrombogenic reaction;
and other proteins such as silk can illicit an immune response.
In alternative embodiments, instead of being made from a bioactive material, the agent carrier 14 is made from a material that adheres or absorbs a bioactive agent. For examples, the agent carrier 14 may include one or more polymer filaments, a sponge, a cloth, a hydrogel, or other materials that are capable of absorbing or adhering a bioactive agent. In this case, the agent carrier 14 is used to deliver the bioactive agent, which will diffuse out of the agent carrier 14 into the surroundings when placed in an aneurysm.

The bioactive agent may also be disposed within the carrier, e.g., wherein the carrier has a sealed reservoir containing the agent, or wherein the agent is dispersed within the material comprising the container. In such embodiments, the agent will diffuse out of the carrier. The selected agent preferably elicits a tissue reaction that leads to rapid in-growth of fibro-cellular tissue, thereby stabilizing the occlusion of the aneurysm. The agent may include any of the materials described previously. The agent may also include drugs, proteins, cells, genetic modifiers, inflammatory agents, immuno-agonistic agents (e.g. Freunds advuvant or squalene), clot stabilizer, clot activators (e.g. thrombin or Factor XI II), cellular materials (e.g.
concentrated blood products, fibroblasts, smooth muscle cells, progenitor cells, genetically engineered cells that secrete a particular bioactive protein), viral vectors, or plasmids.

Claims

1. A vaso-occlusive device, comprising:
an occlusive member having a lumen; and an agent carrier disposed within the lumen, the agent carrier comprising or otherwise carrying a bioactive agent that elicits a biological reaction inside a body.

2. The vaso-occlusive device of claim 2, wherein the agent carrier is secured to the occlusive member.

3. The vaso-occlusive device of claims 1 or 2, wherein the bioactive agent comprises a homopolymer, a copolymer, or a combination thereof.

4. The vaso-occlusive device of claim 3, wherein the bioactive agent comprises one or more of a polyester, acrylic, polyether, polysiloxane, polyurethane and polycarbonate.

5. The vaso-occlusive device of claims 1 or 2, wherein one or both of the agent carrier and bioactive agent comprises one or more of a synthetic polymer, polysaccharide and protein.

6. The vaso-occlusive device of claim 5, wherein one or both of the agent carrier and bioactive agent comprises one or more of polyglycolic acid, polylactic acid, polycaprolactone, polyhydroxyalkanoate, polydioxanone, poly(trimethylene carbonate), polyanhydride, and polyamino acid, and copolymers thereof.

7. The vaso-occlusive device of claim 6, wherein one or both of the agent carrier and bioactive agent comprises one or more of poly(g-ethyl glutamate), poly(DTH iminocarbonate), poly(bisphenol A iminocarbonate), and polyarylate, and copolymers thereof.

8. The vaso-occlusive device of any of claims 1-7, wherein the agent carrier has an elongate shape.

9. The vaso-occlusive device of any of claims 1-7, wherein the occlusive member is a coil.

10. The vaso-occlusive device of claim 9, wherein the agent carrier has a coil shape.

11. The vaso-occlusive device of any of claims 1-10, wherein the agent carrier comprises a material that adheres or absorbs the bioactive material.

12. The vaso-occlusive device of any of claims 1-11, wherein the agent carrier comprises an active element carried in the lumen, wherein the active element

13 expands or contracts when placed in a body to thereby cause the occlusive member to substantially retain its shape when deployed in a body cavity.

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